Skin facts
Protection, body temperature regulation, sensation, vitamin D synthesis, blood reservoir, excretion
What is the primary cell type of the epidermis?
Keratinocytes--> produce keratin
What are the layers of the dermis? Which of these two layers is more superficial?
Reticular layer (deeper and thicker layer of dense irregular CT) and papillary layer (thin superficial layer made of areolar CT)
What are the two basic types of glands in the integumentary system?
Sweat glands and sebaceous glands
What are the body's basic survival needs?
Nutrients, oxygen, water, appropriate temperature, appropriate atmospheric pressure for breathing
What is the function of the hypodermis?
Not part of the skin. It is mostly adipose tissue with some areolar CT. Stores fat, anchors skin to underlying structures (e.g. muscles) loosely enough for skin to slide. Shock absorber and insulator to reduce heat loss.
Name the layers of the epidermis in order from deepest to most superficial
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
What is the significance of the dermal papilla? of the epidermal ridges?
Dermal papillae indent the overlying epidermis and contain capillary loops and free nerve endings.
In thick skin, create epidermal ridges or friction ridges that enhance our grip and sense of touch
Describe the structure and function of sebaceous glands.
Simple branched alveolar glands that secrete an oily substance called sebum that softens and lubricates the hair and skin and slows water loss from the skin. It is bactericidal
Give an example of a physiologic variable whose level is normally maintained through a negative feedback mechanism.
Insulin (blood sugar regulation), thermoregulation
What is the function of melanin?
Form a pigment shield to protect the nucleus from the damaging effects of UV radiation in sunlight
What is the difference between thin skin and thick skin? Where is thick skin found?
Thin skin does not have stratum lucidum with thinner strata. Thick skin is found on the palms, soles of feet, fingertips
What forms the lines of cleavage and what is the significance of them?
Less dense regions of collagen. When an incision is made parallel to these lines, the skin gapes less and heals more rapidly
Which type of sudoriferous gland secretes into hair follicles? into ducts that open in a pore on the skin’s surface?
Hair follicles: apocrine
opening in skin's surface: eccrine
What is the ABCDE mnemonic?
Key detection points of melanoma
A- asymmetry (irregular shape)
B- border (irregular and jagged)
C-Color (is color uneven)
D- Diameter (>6mm)
E- Evolving (getting bigger or more irregular over time)
Name the components of the Braden Scale?
Sensory perception, moisture, activity, mobility, nutrition, friction and shear
In which layer do cells begin to die? Why do they die?
Stratum granulosum due to lack of nutrients. Epidermis is avascular and relies on the dermis for nutrients. Above the stratum granulosum, the epidermal cells are too far from the dermal capillaries and the glycolipid coating cuts them off from nutrients
How does sunlight affect melanocytes?
When we expose our skin to sunlight, keratinocytes secrete chemicals that stimulate melanocytes. Prolonged sun exposure causes a substantial melanin buildup, which helps protect the DNA of skin cells from UV radiation by absorbing the rays and dissipating the energy as heat. Indeed, the initial signal for speeding up melanin synthesis seems to be a faster repair rate of DNA that has suffered photodamage
Where do the ducts of most sebaceous glands terminate?
Found all over the body except in the thick skin of palms and soles. Small on the body trunk and limbs, but quite large on the face, neck, and upper chest.
Most, but not all, sebaceous glands develop as outgrowths of hair follicles and secrete sebum into a hair follicle, or occasionally to a pore on the skin surface. Arrector pili contractions force sebum out of the hair follicles to the skin surface.
What are the four classes of connective tissues?
Connective tissue proper (loose and dense CT), Cartilage, Bone, and Blood
Identify and describe the four steps involved in the regeneration of tissue after injury.
2. Migratory phase (migration of cells from stratum basale into the epidermal area of injury; fibroblast migrate to regenerate damaged hypodermis/dermis; blood clot replaced by granulation tissue)
3. Proliferative phase: tissue and blood continue to regenerate and the scab detaches, epithelium thickens
4. Maturation phase: epidermis fully regenerated and fibroblast decrease in number
In which layer do cells contain keratohyalin and lamellar granules? What is the functional significance of each of these granule types?
Stratum granulosum.
Keratohyalin: form keratin in upper layers
Lamellar: contain water-resistant glycolipid secreted into extracellular space. Makes epidermis water-resistant
What types of cells and connective tissue fibers are commonly found in the dermal layer?
Collagen fibers and smaller amounts of elastic and reticular fibers
Cells: fibroblasts, macrophages, mast cells, WBCs
What is the difference between the two types of sudoriferous glands?
Eccrine sweat glands are more numerous and secretes a hypotonic filtrate of blood that is released by exocytosis to prevent the body from overheating.
Apocrine sweat glands are largely confined to the axillary and anogenital areas and start during puberty. Also use exocytosis to secrete similar substance to sweat with more fatty substances and proteins.
What are two basic components of all connective tissues?
Extracellular matrix (CT mainly composed of ECM--> can bear weight, withstand great trauma and tension
Common origin: All CT arise from mesenchyme